A sample of grape juice has a hydroxide ion concentration of 1.4 × 10-10 M. Is the grape juice more or less acidic than a sample of orange juice that has a hydronium ion concentration of 1.8 × 10-4 M? To compare the acidity of the orange juice and grape juice, compare the hydronium ion concentrations and/or pH values of the two solutions. How does the acidity of a solution vary with hydronium ion concentration and pH?